Question

the diagram below shows the general pattern of air circulation in the atmosphere. many of the worlds deserts are located at latitudes slightly below 30° n. this includes the region marked with an x on the map. which of the following statements best explains this? a. the air descending from the upper atmosphere contains very little moisture. b. moist air near the equator tends to flow away from land and toward the oceans. c. air near the equator moves quickly as earth rotates, so it cannot carry much moisture.

Explanation:

At around 30°N (and 30°S), there is a descending air current in the atmospheric circulation pattern. As air descends, it warms (adiabatic warming). When air warms, its capacity to hold moisture increases, but since it is descending (not rising and cooling to condense moisture for precipitation), the descending air has lost much of its moisture (after precipitation in equatorial regions where air rises). So, the region has dry conditions, favoring desert formation.

• Option B is incorrect because moist air near the equator (which is rising air, not flowing away from land in a way that directly causes deserts at 30°N).
• Option C is incorrect because air near the equator (due to Earth's rotation - Coriolis effect) has distinct circulation patterns (rising air in Hadley cells), and it's not about the speed preventing moisture - holding (rising equatorial air can hold and release moisture as it cools at higher altitudes).

Answer:

A. The air descending from the upper atmosphere contains very little moisture.